1 chapter 4 lipids: fats and oils. 2 lipids fats oils cholesterol lecithin
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Functions of Lipids
Insulation Cushion around critical organs Provides energy (adipose cells = compact
energy storage) Protein-sparing Part of all cell membranes Transport of fat-soluble vitamins Essential fatty acids
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In food, fat enhances:
Taste Flavor Aroma Crispness Juiciness Tenderness
Smooth texture Creamy feeling Feeling full
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Triglycerides in Food
Fruits and vegetables Breads, cereals, rice, pasta, and grains Dry beans and peas, nuts and seeds Meat, poultry, fish Dairy foods Fats, oils, and condiments
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3 Types of Triglycerides
1. Saturated triglycerides (saturated fat) ANIMAL FOODS
Cheese Beef Whole milk Fats in baked goods Butter Margarine
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3 Types of Triglycerides
2. Monounsaturated Fats
Olive oil Canola oil Peanut oil Margarine made with
canola oil or other highly monounsaturated fat
Olive Oil
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3 Types of Triglycerides
3. Polyunsaturated Fats Safflower oil Corn oil Soybean oil Sesame oil Sunflower oil Nuts and seeds
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Trans Fatty Acids
Occur naturally at low levels in meat and dairy foods.
Trans fats we eat are often due to hydrogenation of vegetable oils to make shortening, margarine, and fats for frying.
Trans fats raise blood cholesterol levels as much as saturated fat.
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Main Contributors to Trans Fats in Diet
Cakes, cookies, pies, bread, etc. 40% of
trans fats eaten Animal products 21% Margarine 17% Fried potatoes 8% Potato chips, corn chips, popcorn 5% Household shortening 4%
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Essential Fatty Acids
Linoleic acid is an omega-6 fatty acid found in vegetable oils, whole grains, and vegetables.
Alpha-linolenic acid is the leading omega-3 fatty acid found in food, and it is found in canola, flaxseed, soybean, walnut, and wheat germ oils. Other good sources include ground flaxseed, walnuts, and soy products.
The body converts alpha-linolenic into DHA and EPA (also omega-3s). DHA and EPA are found in fatty fish such as salmon and mackerel.
Americans get more than enough linoleic, but not enough alpha-linolenic.
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Essential Fatty Acids (cont’d)
Both EFAs: Are vital to normal growth and development in infants
and children, Maintain the structural parts of cell membranes Have a role in the proper functioning of the immune
system Are used to make eicosanoids.
Eicosanoids made from linoleic acid tend to increase blood pressure, blood clotting, and inflammation.
Eicosanoids made from alpha-linolenic acid dilate blood vessels and reduce blood clotting and inflammation.
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Rancidity
Deterioration of fat, resulting in undesirable flavors and odors.
Saturated fats are more resistant to rancidity than unsaturated fats.
Rancidity is hastened by heat and ultraviolet light.
To prevent rancidity, store fats and oils tightly sealed in cool, dark places.
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Cholesterol
An odorless, white, waxy, powdery substance.
Cholesterol is present in every cell in your body. It is needed to make bile acids, to make cell membranes, many hormones (such as sex hormones), and vitamin D.
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Cholesterol (cont’d)
Cholesterol is found only in foods of animal origin: egg yolks, meat, organ meats, poultry, fish, milk, and milk products. Lower-fat milk products contain less cholesterol than full-fat milk products.
We take in about 200 to 400 milligrams of cholesterol daily and the liver and body cells also make cholesterol (about 700 milligrams), therefore it is not an essential nutrient.
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Lecithin
A phospholipid. Functions as a vital component of cell
membranes. Also acts as an emulsifier.
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Digestion, Absorption, & Metabolism
Mouth – Lingual lipase. Stomach – Gastric lipase. Intestine
Bile acids Pancreatic lipase Intestinal lipase
Once absorbed, triglycerides are reformed.
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Lipoproteins
Protein-coated packages that carry fat and cholesterol through the bloodstream.
Chylomicron
Very low-density lipoprotein (VLDL)
Low-density lipoprotein (LDL)
High-density lipoprotein(HDL)
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Lipids and Health
Heart disease Too much circulating cholesterol leads to
plaque and atherosclerosis Angina Myocardial infarction Stroke
Main source of cholesterol buildup: LDL
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Lipids and Health (cont’d.)
What affects cholesterol levels? Saturated fat, trans fat, and cholesterol in diet Mono- and polyunsaturated fat in diet Weight Physical activity Age and gender Heredity
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Lipids and Cancer
Cancer is the second leading cause of death in the U.S.
Fat may be involved in certain cancers such as prostate cancer.
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Dietary Recommendations for Fat
No RDA or AI for total fat (except for infants), saturated fat, cholesterol, or trans fats.
AMDR for total fat 1–3 years old 30-40% of kcal 4–18 years old 25-35% of kcal Over 18 years old 20-35% of kcal
AI set for essential fatty acids. DGA and AHA recommend 10% or less from sat. fat,
less than 300 mg of cholesterol daily, and replace sat fats with poly and mono fats such as fish and nuts.
If fat intake is higher than 30%, use monounsaturates.
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Percentage of Kcal From Fat &Percentage of Fat By Weight
Percentage of kcalories from fat 27 kcal from fat x 100 = 19 percent
140 kcal Percentage of fat by weight
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Fat Substitutes
Water Carbohydrate-based
Cellulose gel Carrageenan Polydextrose Starch Modified food starch Dextrins and maltodextrins Gums
Protein-based – Simplesse Fat-based – Olestra